Direct-fired heating system

Abstract

A direct gas-fired heating unit is provided which uses an axial-bladed fan for generating a main air flow through a burner unit. The burner unit has a dedicated combustion air blower supplying combustion air to the burner separate from a main air flow generated by the main fan. The burner unit includes a dedicated blower which draws a small volume of outside air as combustion air. Further, the burner unit may include bypass ports which allows for discharge of bypass air from the burner unit.

1 . A direct fired heating unit comprising;
 a filter/fan section which draws in air with an energy-efficient axial-bladed fan generating a main air flow;   a middle section containing a burner unit having a burner generating a burner flame for heating said main air flow and a dedicated combustion air blower supplying a flow of combustion air to the burner which said combustion air is isolated from said main air flow;   a burner section where said burner flame and main air flow mix; and   a discharge plenum which discharges and distributes the heated air to the building space.   
     
     
         2 . The heating unit according to  claim 1 , wherein said burner unit solely uses said combustion air for flame generation and does not rely upon the main air flow from the main fan for combustion air. 
     
     
         3 . The heating unit according to  claim 3 , wherein said blower relies solely upon said dedicated blower which draws in a relatively small volume of outside air and feeds same directly to the burner flame. 
     
     
         4 . The heating unit according to  claim 1 , wherein said burner unit has a gas-fed burner which generates said flame between two angled mixing plates wherein the burner flame is formed on the interior side of the mixing plates, and said combustion air is supplied to the outside of the mixing plates wherein the mixing plates include perforations to allow for controlled passage of air flow into the flame region. 
     
     
         5 . The heating unit according to  claim 4 , wherein said burner unit further includes a containment box surrounding the mixing plates and said burner which isolates the combustion air flow from the surrounding main air flow. 
     
     
         6 . The heating unit according to  claim 1 , wherein said burner is supplied with a piped supply of outside combustion air by said air blower. 
     
     
         7 . The heating unit according to  claim 6 , wherein said outside air makes up only 1-5% of the heating unit air flow since said outside air is directly piped to the burner. 
     
     
         8 . The heating unit according to  claim 1 , wherein said burner unit is positioned in the main air flow downstream of the main fan wherein the flame forms in the burner section, with the main air flow flowing upwardly from the filter/fan section through the burner section for heating, and then to the discharge plenum, said main air flowing directly over and about the burner housing and flame for direct heating of the air flow. 
     
     
         9 . The heating unit according to  claim 1 , wherein said filter/fan section includes said axial bladed fan on a colder upstream side of said burner which generates said main air flow. 
     
     
         10 . The heating unit according to  claim 1 , wherein all of said blower air flow is supplied at a rate which supplies the necessary flow of said combustion air. 
     
     
         11 . A direct fired heating unit comprising;
 a filter/fan section which draws in air with an energy-efficient axial-bladed fan generating a main air flow;   a middle section containing a burner unit having a burner generating a burner flame for heating said main air flow and a dedicated air blower supplying a flow of blower air along a blower air flow path to the burner which said blower air is isolated from said main air flow upstream of said burner unit;   a burner section where said burner flame and main air flow mix;   a discharge plenum which discharges and distributes the heated air to the building space; and   a first portion of said blower air comprising combustion air supplied to said burner and a second portion of said blower air being diverted back into said main air flow as a bypass air flow.   
     
     
         12 . The heating unit according to  claim 11 , wherein the flow path of said blower air is provided with one or more exit ports that allow for said second portion of said blower air flow to divert to said main air flow as said bypass air flow, while said second portion of said blower air flow continues to the burner as the combustion air flow. 
     
     
         13 . The heating unit according to  claim 12 , wherein said burner unit includes a chamber which includes first passages supplying the combustion air to said burner and second passages defining said exit ports exiting from said chamber to discharge said bypass air flow to said main air flow. 
     
     
         14 . The heating unit according to  claim 13 , wherein said bypass air flow allows the concentration of combustion byproducts to be maintained at a low level that satisfies environmental regulations. 
     
     
         15 . The heating unit according to  claim 13 , wherein said exit ports have controllable openings which control the amount of said bypass air flow.